That can be a loaded question, because all the cars out there are competivie given the right driver. I feel the Xray NT1 is hard to beat. Xray always makes a solid product (kind of pricey), but they are good cars with great support. If the new Mugen MTX5 is anything like its older brother (MRX5) then it will be a solid car as well. There are also the Serpent 733, Capricorn, Shepherd Velox V10, Kyosho R4 and I'm sure some others that I'm missing
I would go to your local track and see what most of the racers are running. Local part support is always nice and they can help you with setup and so on.
On the other hand if you’re like me, then you enjoy running a car different from everyone else. I would only recommend this if you enjoy a challenge